1. Field of the Invention
The present invention is directed to a safety mechanism for a hoist having a lowering speed limit. The safety mechanism is activated as the speed of the load exceeds the lowering limit by a latch which locks the ratchet wheel which is rotating with the cable drum of the hoist. The ratchet wheel has a brake lining against the cable drum.
2. Description of the Background Art
U.S. Pat. No. 4,520,998 shows a safety mechanism as described above. In this system, the drum is braked with a very high braking force in the beginning of the stopping because the brake linings may get stuck in the drum before the safety mechanism is activated. Therefore the detaching force may have a very high value before the brake lining of the ratchet wheel begins to slide on the surface of the drum. The ropes may also be weakened during over time and therefore it is possible that the ropes may be broken when the braking force is very high. The ropes should bear a force that is needed to decelerate a maximum load from a certain speed within a predetermined distance. The braking moment should not exceed this force in any situation.